/* bootstrap UI组件的样式扩展 */
._nav_bg {
	/* background-color: #ccc; */
	border-bottom: 1px solid #eee;
	padding: 0;
}

._nav_bg .navbar-brand {
	margin-right: 0;
}

._nav_bg.navbar-dark .navbar-nav .nav-item {
	position: relative;
}

._nav_bg.navbar-dark .navbar-nav .nav-item .nav-link {
	color: #666;
	transition: all 0.3s;
}

.navbar-dark .navbar-toggler {
	color: #002557;
	border-color: #002557;
}

.navbar-dark .navbar-toggler-icon {
	background-image: url(../images/open_icon.png);
}

@media screen and (min-width: 990px) {
	._nav_bg {
		justify-content: space-between;
		max-width: 64rem;
		margin: 0 auto;
	}

	._nav_bg .navbar-collapse {
		flex-grow: inherit;
	}

	._nav_bg.navbar-dark .navbar-nav .nav-item {
		padding: 0;
	}

	._nav_bg.navbar-dark .navbar-nav .nav-item {
		border-left: 1px solid #eee;
	}

	._nav_bg.navbar-dark .navbar-nav .nav-item:last-child {
		border-right: 1px solid #eee;
	}

	._nav_bg.navbar-dark .navbar-nav .nav-link {
		padding: 30px 20px;
		text-align: center;
	}
	._nav_bg.navbar-dark .navbar-nav .nav-item::after {
		content: "";
		position: absolute;
		height: 4px;
		width: 100%;
		left: 0;
		bottom: 0;
		background-color: #002557;
		opacity: 0;
		transition: all 0.4s;
	}
	._nav_bg.navbar-dark .navbar-nav .nav-item:hover:after {
		opacity: 1;
	}
	._nav_bg.navbar-dark .navbar-nav .nav-item.active:after {
		opacity: 1;
	}
	._nav_bg.navbar-dark .navbar-nav .nav-item.active .nav-link {
		color: #002557;
	}
	._nav_bg.navbar-dark .navbar-nav .nav-item:hover .nav-link {
		color: #002557;
	}
}

@media screen and (max-width: 990px) {
	._nav_bg {
		padding: 0.5rem 0;
	}
	._nav_bg .navbar-brand {
		margin-left: 1.3rem;
	}
	.navbar-dark .navbar-toggler {
		margin-right: 1.3rem;
	}
	.navbar-collapse {
		padding: 0 1.3rem;
		background-color: #002557;
	}
	._nav_bg.navbar-dark .navbar-nav .nav-item .nav-link {
		color: #efefef;
	}
}
